RU2548604C2 - Piezoelectric and/or pyroelectric composite solid material, method of obtaining thereof and thereof application - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to piezoelectric and/or pyroelectric composite material. Essence: material includes dielectric matrix (11), filler from at least one inorganic piezoelectric and/or pyroelectric material. Filler includes thread-like nanoparticles (12), distributed on the entire volume of solid dielectric matrix (11) with amount by volume less than 50%. Main elongation directions of fibre-like nanoparticles (12) of inorganic filler, distributed in dielectric matrix (11), have in fact isotropic distribution in solid dielectric matrix (11). Invention also relates to method of manufacturing and application of such hybrid material for production of construction components and films on carrier, obtained by precipitation on such substrate surface.

EFFECT: high piezoelectric and/or pyroelectric response with reduced part of functional filler, provision of combination of plasticity, strength and low dielectric permeability of organic polymer materials with electrically active properties of inorganic piezoelectric and/or pyroelectric materials, low intensity of electric field at polarisation.

21 cl, 3 dwg

Description

The invention relates to a piezoelectric and / or pyroelectric composite solid material, to a method for its preparation and to the use of such a material.

The invention finds its application in the field of acoustic transducers, piezoelectric resonators, pressure and / or acceleration sensors, drives, especially direct actuators (drives), capable of generating movement steps from 0.1 to 100 microns, in particular for atomic force microscopy and scanning tunneling microscopy, in piezoelectric motors, piezoelectric generators and transformers, pyroelectric sensors, soundproof materials, in particular anechoic piezoelectric materials, mat Series having a high dielectric constant, in particular for electronics and electrical engineering, and materials of piezoelectric drives.

It has already been proposed to include fillers of micrometric or nanometric particles of the PZT type ferroelectric material (zirconate and lead titanate), in particular in the form of spherical nanoparticles, i.e. nanoparticles with an aspect ratio of approximately 1 into a polyepoxymatrix to form a piezoelectric composite material (see, for example, "Furukawa et al., (1976), Japanese Journal of Applied Physics, 15; 11, 2119-2129"). Such essentially spherical particles do not allow reaching a state of sufficiently high conductivity in a composite material with a degree of filling that is sufficiently low and suitable for maintaining mechanical properties - mechanical impact resistance, flexibility and ductility - matrix.

The use of PMN-PT piezoelectric particles (lead / magnesium / niobium-lead / titanium) with substantially spherical morphology is also known (see, for example, "Lam et al., (2005), Composite Science and Technology, 65, 1107-1111 ") in a polymer matrix in a volume ratio of 5% to 40%. Such a composite makes it possible to achieve a piezoelectric coefficient of 10 to 30 pC / N, but does not significantly preserve the initial plasticity of the matrix.

Therefore, the task is to obtain a composite solid material with a high piezoelectric effect and / or pyroelectric effect, especially with piezoelectric and / or pyroelectric efficiency, which is greater than the corresponding efficiency of piezoelectric and / or pyroelectric composite materials from the prior art, but without a significant deterioration in the mechanical properties of the composite solid material compared with the mechanical properties of the matrix constituting the specified composite solid material.

The maximum piezoelectric effect and / or pyroelectric effect is actually obtained due to the amount by volume of more than 25%, usually approximately 50%, which significantly modifies the mechanical properties of the obtained composite material relative to the mechanical properties of the matrix forming the specified composite solid material.

The invention is aimed at eliminating the disadvantages mentioned above by creating a composite solid material, which, on the one hand, has the advantages of composite materials relative to inorganic ferroelectric (ceramic) materials in terms of mechanical properties (especially greater lightness with at least equivalent particular superior flexibility, ductility and impact resistance), but which, on the other hand, has:

- dielectric constant (ε), which is as low as possible, in particular, significantly less than 20, and

- a piezoelectric efficiency indicator g ₃₃ (d ₃₃ / ε) of more than 45 mV · m / N, where d ₃₃ is the piezoelectric coefficient of the composite material, and / or

- pyroelectric efficiency indicator F (p / ε) of more than 0.7 μC / K / m ² , where p is the pyroelectric coefficient of the composite material.

The invention provides such a piezoelectric and / or pyroelectric composite solid material, which has a reduced degree of filling, suitable for substantially preserving the mechanical properties of the specified composite solid material.

The invention also proposed such a composite solid material of reduced density with piezoelectric and / or pyroelectric efficiency, which is at least preserved and, in particular, increased.

The invention also relates to such a piezoelectric composite solid material suitable for providing increased elastic deformations at a given load and an increased piezoelectric response to said load.

The invention also relates to such a composite solid material that maintains a high piezoelectric and / or pyroelectric response, having a fraction of functional filler reduced compared to composite materials from the prior art.

The invention, in particular, relates to a composite solid material, which, unlike organic piezoelectric and / or pyroelectric materials, does not require the use of an intense electric field, which can cause a dielectric breakdown of said organic material, in order to polarize said organic piezoelectric and / or pyroelectric material.

Accordingly, the invention provides a composite solid material having mechanical properties comparable to the mechanical properties of polymeric materials of the same nature, and at the same time, a piezoelectric efficiency index d _{33 of} more than 45 mV · m / N.

The invention also provides a composite solid material having mechanical properties comparable to the mechanical properties of composite insulating materials of the same nature, and at the same time, a pyroelectric efficiency index F of more than 0.7 μC / K / m ² .

The invention also provides a composite solid material having flexibility, ductility and ease of use that are substantially equivalent to these properties of the polymer matrix, and at the same time also the electroactive properties of the inorganic functional filler.

The invention also provides such a composite solid material having improved dispersion properties of vibrational energy, in particular sound energy, in the form of heat.

The invention accordingly relates to a composite solid material having the properties of plasticity, mechanical strength and low dielectric constant of organic polymeric materials, at the same time having the electroactive properties of inorganic piezoelectric and / or pyroelectric materials and especially low electric field intensity necessary for its polarization.

More preferably, the invention provides a composite solid material having a solid (homogeneous or composite) matrix of electrical insulation material and a piezoelectric efficiency index d _{33 of} more than 45 mV · m / N and / or a pyroelectric efficiency indicator F of more than 0.7 μC / K / m ² , where the final mechanical properties of the composite solid material according to the invention are at least 90% of the mechanical properties of the solid matrix.

The invention also provides a composite solid material having a piezoelectric efficiency index d _{33 of} greater than 45 mV · m / N, but in which the excess charge associated with the functional filler of the piezoelectric and / or pyroelectric nanoparticles in the composite solid material does not substantially exceed 50% .

The invention also relates to a method for producing such a composite solid material, which is simple, inexpensive and quick to implement, does not require any special equipment and protects the environment.

The invention also provides a method for producing parts of any shape having various material compositions.

Thus, the invention relates to a piezoelectric and / or pyroelectric composite solid material called a hybrid material containing:

- solid dielectric matrix,

- inorganic filler distributed in a solid dielectric matrix, where the specified inorganic filler consists of a material selected from the group consisting of piezoelectric materials, pyroelectric materials and piezoelectric and pyroelectric materials,

wherein said inorganic filler comprises solid nanoparticles called filamentous nanoparticles having:

- length, continuing in the main direction of elongation of filiform nanoparticles,

two sizes, called orthogonal dimensions, extending in two transverse directions that are mutually perpendicular and orthogonal to the indicated main direction of elongation of the filamentary nanoparticles, where the indicated orthogonal dimensions are less than the specified length and less than 500 nm, and

- two ratios, called aspect ratios (also called characteristic ratios), between the specified length and each of the two orthogonal sizes, where the specified aspect ratios are more than 10,

where these filamentary nanoparticles are distributed in the volume of the solid dielectric matrix in an amount by volume of less than 50%, especially from 0.5% to 50%, preferably from 5% to 20%, in particular approximately 12%, and where

the main directions of elongation of filiform nanoparticles of an inorganic filler distributed in a dielectric matrix have a substantially isotropic distribution in a solid dielectric matrix.

In the hybrid material of the invention, the solid dielectric matrix may preferably be formed from at least one material selected from the group of organic materials, i.e. materials consisting of at least one organic compound having at least one covalent bond formed between a carbon atom and an atom other than carbon (in particular hydrogen).

In the hybrid material of the invention, the solid dielectric matrix is preferably formed from a synthetic organic polymer material.

Preferably, the solid dielectric matrix of the hybrid material according to the invention comprises a material selected from the group of organic materials consisting of at least one organic compound containing at least one silicon atom.

Preferably, the solid dielectric matrix of the hybrid material according to the invention is selected from the group consisting of piezoelectric solid dielectric matrices, pyroelectric solid dielectric matrices and solid dielectric matrices which are electrically neutral.

Preferably and according to the invention, the solid dielectric matrix of the hybrid material is a continuous matrix in which said whisker nanoparticles are distributed throughout the volume of said solid dielectric matrix.

Preferably, the inorganic filler of the hybrid material according to the invention is formed from a non-polymer metal compound not containing carbon.

In the hybrid material according to the invention, the aspect ratio of the filamentous nanoparticle is the ratio between the length of the filamentous nanoparticle and one of its two dimensions orthogonal to the specified length. As an example, an aspect ratio of 100 for a filamentous nanoparticle of a conventional circular cylindrical shape means that its length is substantially equal to its 100-fold average diameter. In any case, the filiform nanoparticle has the usual elongated shape, in which the ratio of its largest size (its length) to each of the two orthogonal sizes is more than 10.

The inventors observed that the hybrid material according to the invention, in which the inorganic filler is formed from filamentous nanoparticles consisting of a piezoelectric and / or pyroelectric material, where said filamentous nanoparticles have a high aspect ratio and are distributed in the volume of the solid dielectric matrix in an amount by volume of less than 50% has an increased bending strain of filiform nanoparticles, an increased charge separation of the piezoelectric and / or pyroelectric material having Exposure to extreme aspect ratio and a larger piezoelectric and / or pyroelectric effect for the same load applied to said hybrid material.

Preferably, the filamentary nanoparticles are distributed in the volume of the solid dielectric matrix in an amount by volume of less than 35%, especially from 1% to 35%, preferably from 5% to 30%.

More preferably, the hybrid material of the invention is preferably characterized by at least one of the following features:

two orthogonal sizes of filamentary nanoparticles are from 50 nm to 500 nm, in particular approximately 200 nm,

whisker nanoparticles have two aspect ratios of more than 10, especially more than 100, in particular approximately 250,

whisker nanoparticles have a length of more than 1 μm, especially from 2 μm to 50 μm, in particular about 10 μm,

- two orthogonal sizes of filamentary nanoparticles are the cross-sectional diameter of filamentous nanoparticles,

the inorganic filler of the hybrid material according to the invention is formed from a material selected from the group consisting of inorganic piezoelectric ceramics, pyroelectric ceramics and piezoelectric and pyroelectric ceramics,

the inorganic filler of the hybrid material according to the invention is formed from a material selected from the group of inorganic ceramics, especially perovskite-type ceramics, for example barium titanate of the formula BaTiO ₃ , lead zirconate titanates (PZT) of the formula PbZr _x Ti _-1-x O ₃ , Ba _x Sr _{1- x} TiO ₃ , Ca _x Sr _1-x TiO ₃ , BaTi _x Zr _1-x O ₃ , where x is a real number that may be zero or 1, or from 0 to 1, SrTiO ₃ , BaZrO ₃ , SrZrO ₃ , PbTiO ₃ , KNbO ₃ , LiNbO ₃ , PMN-PT (Pb / Mg / Nb-Pb / Ti), barium dithitanate (BaTi ₂ O ₅ ) and niobate (NaNbO ₃ ),

a solid dielectric matrix of a hybrid material contains at least one polymer material selected from the group consisting of thermoplastic polymer materials and thermosetting polymer materials,

- a solid dielectric matrix of a hybrid material is formed of an organic polymer material selected from the group consisting of piezoelectric materials, pyroelectric materials and piezoelectric and pyroelectric materials. For example, the organic polymer material of a solid dielectric matrix is selected from the group consisting of PVDF (polyvinylidene fluoride, Russian-language abbreviation - PVDF), PVDF-TrFE (copolymer of polyvinylidene fluoride with trifluoroethylene), fluorinated terpolymers (copolymers formed from three different monomeric units), odd PEEK (polyetheretherketone, Russian-language abbreviation - PEEK), even polyamides, polyurethanes and silicones.

Preferably, the hybrid material has a low dielectric constant, in particular less than 20, and a piezoelectric efficiency index g _{33 of} more than 45 mV · m / N and / or a pyroelectric efficiency index F of more than 0.7 μC / K / m ² and final mechanical properties that are essentially retained (especially to a degree of more than 90%) compared to a solid dielectric matrix.

Preferably and according to the invention, the inorganic filler is distributed substantially uniformly in the solid dielectric matrix. The substantially uniform distribution of the inorganic filler in the solid dielectric matrix means that the average distance separating adjacent filamentary nanoparticles is substantially constant throughout the volume of the solid dielectric matrix.

Preferably, and according to the invention, the filamentary nanoparticles are selected from the group consisting of nanowires, nanorods and nanotubes.

In a first embodiment of the hybrid material of the invention, the whisker nanoparticle within the scope of the invention is a nanorod or nanowire. In this first embodiment, the two orthogonal sizes of the whisker nanoparticles are the diameter of its cross section. The filamentous nanoparticle can also be a tape, where the two orthogonal sizes of the filamentous nanoparticles according to the invention are its width (first orthogonal size) and its thickness (second orthogonal size).

In a second embodiment of the hybrid material according to the invention, the filamentary nanoparticles within the scope of the invention can also be nanotubes formed from a hollow cylinder having a wall thickness of less than 100 nm.

Preferably, according to the invention, when the whisker nanoparticles are nanotubes, the whisker nanoparticles have a wall thickness forming said nanotube of substantially less than 100 nm.

Preferably and according to the invention, the main directions of elongation of filiform nanoparticles of an inorganic filler distributed in a dielectric matrix have a substantially isotropic distribution in a solid dielectric matrix. By a substantially isotropic distribution of the main directions of elongation of the whisker nanoparticles in a solid dielectric matrix, it is understood that the main directions of elongation of whisker nanoparticles, on average, do not have a preferred orientation in the solid dielectric matrix, but instead extend equally in all directions.

Preferably, the filamentary nanoparticles distributed in the dielectric matrix have a substantially homogeneous distribution in the solid dielectric matrix.

In addition to this, the inventors also found that such a hybrid material in which nanoparticles having a high aspect ratio are distributed isotropically and homogeneously in a solid dielectric matrix in a volume ratio of less than 50% ensures the deformability of said nanoparticles and the coherence between said nanoparticles which are sufficient to obtain the desired piezoelectric and / or pyroelectric effects. In particular, the inventors have observed that such a volume fraction of whisker nanoparticles provides sufficient connectivity between whisker nanoparticles to provide conduction by interaction between whisker nanoparticles with a small fraction of said whisker nanoparticles.

Preferably and according to the invention, the hybrid material further comprises a filler called a conductive filler, an electrically conductive material containing conductive nanowires, having:

- a length extending in the main direction of elongation of the conductive nanowires,

two sizes, called orthogonal dimensions, extending in two transverse directions that are mutually perpendicular and orthogonal to the indicated main direction of elongation of the conductive nanowires, where said orthogonal dimensions are less than the specified length and less than 500 nm, and

- two ratios, called aspect ratios, between the specified length and each of the two orthogonal dimensions of the conductive nanowires, where the specified aspect ratios are more than 50,

wherein said conductive nanowires are distributed in a volume of a solid dielectric matrix in an amount by volume of less than 1%, in particular substantially approximately 0.5%.

In an embodiment, preferably according to the invention, such a piezoelectric and / or pyroelectric hybrid material according to the invention is characterized by at least one of the following features:

- two orthogonal sizes of conductive nanowires are from 50 nm to 300 nm, in particular approximately 200 nm,

- conductive nanowires have a length of more than 1 μm, especially from 30 μm to 300 μm, in particular approximately 50 μm,

- two orthogonal dimensions of the conductive nanowires represent the cross-sectional diameter of the conductive nanowires,

- conductive nanowires have two aspect ratios of more than 50, in particular approximately 250,

- conductive nanowires selected from the group consisting of nanorods and nanotubes, especially carbon nanotubes,

- conductive nanowires are formed from a material selected from the group consisting of gold, silver, nickel, cobalt, copper and their alloys in an unoxidized state,

- conductive nanowires are formed from non-oxidized metal material,

- it contains conductive nanowires in an amount of from 0.1% to 1% by volume.

Preferably, the number of conductive nanowires in the hybrid material is adjusted so that, in the context of the volume fraction, it is below the threshold of electrical percolation in the solid dielectric material used.

Preferably and according to the invention, conductive nanowires are used, the two aspect ratios of which are more than 50, in particular from 50 to 5000, more preferably from 100 to 1000, especially and preferably about 250.

Preferably and according to the invention, the mass fraction of the conductive nanowires relative to the solid dielectric matrix is more than 0.014%.

The invention extends to a method for producing a hybrid material according to the invention.

The invention also relates to a method for producing a composite solid material called a hybrid material, in which a dispersion of an inorganic filler containing filamentous nanoparticles formed from an inorganic material selected from the group consisting of piezoelectric materials, pyroelectric materials and piezoelectric and pyroelectric materials and possibly conductive nanowires is obtained where these filamentary nanoparticles have:

a length extending in the main direction of elongation of filiform nanoparticles,

two sizes, called orthogonal dimensions, extending in two transverse directions that are mutually perpendicular and orthogonal to the indicated main direction of elongation of the filamentary nanoparticles, where the indicated orthogonal dimensions are less than the specified length and less than 500 nm, and

- two ratios, called aspect ratios, between the length and each of the two orthogonal sizes, where the specified aspect ratios are more than 10,

in the liquid composition of the precursor of solid dielectric material so as to obtain an amount by volume of whisker nanoparticles in said hybrid material of less than 50%, and so that the main directions of elongation of whisker nanoparticles of the inorganic filler distributed in the dielectric matrix have a substantially isotropic distribution in the solid dielectric matrix .

Preferably and according to the invention:

a dispersion of whisker nanoparticles and possibly conductive nanowires is obtained in a liquid solvent medium,

the dispersion is mixed into a liquid precursor composition,

the liquid solvent is removed and

the hybrid material is placed in an electric field suitable for polarizing whisker nanoparticles and converting them into piezoelectric and / or pyroelectric whisker nanoparticles.

The polarization step of filamentous nanoparticles from a hybrid material is carried out by methods that are known per se to a person skilled in the art and are suitable for ensuring the conversion of filamentous nanoparticles into filamentous nanoparticles having, on a macroscopic scale, piezoelectric and / or pyroelectric properties.

Preferably according to the invention, when the solid dielectric matrix contains at least one polymer material, then the liquid precursor composition is a solution of the specified polymer material in a liquid solvent selected from a dispersion solvent of filamentous nanoparticles, and possibly conductive nanowires, and solvents that are mixed with the solvent a dispersion of filamentous nanoparticles. Preferably, the liquid precursor composition is a dilute solution of said polymeric material in a liquid solvent.

Preferably according to the invention, when the solid dielectric matrix contains at least one thermoplastic material, then the liquid precursor composition is formed from the solid dielectric matrix in the molten state. Preferably, the liquid precursor composition is a condensed solution of said polymeric material.

Preferably, a dispersion of said inorganic filler containing whisker nanoparticles in said liquid solid dielectric matrix precursor composition is prepared by any means known per se to one skilled in the art, especially by extrusion in twin screw mixers.

Preferably according to the invention, when the solid dielectric matrix contains at least one thermoset material, then the liquid precursor composition is formed from at least one liquid composition included in the thermoset material composition.

Preferably, the dispersion of filamentous nanoparticles and optionally conductive nanowires is obtained in a liquid solvent, said dispersion is mixed into a liquid precursor composition, and the liquid solvent is removed. Said liquid solvent is preferably selected from solvents which are not capable of oxidizing conductive nanowires or which are capable of oxidizing them only partially and in a limited manner.

In addition, it is preferable and according to the invention, when the solid dielectric matrix contains at least one polymer material, then the liquid precursor composition is a solution of the specified polymer material in a liquid solvent selected from a solvent of a dispersion of filamentous nanoparticles, solvents that are mixed with a solvent of a dispersion of filamentous nanoparticles . The dispersion of filamentous nanoparticles can preferably be included in said liquid precursor composition during the step of producing a solid dielectric matrix.

In addition, preferably and according to the invention, the dispersion of whisker nanoparticles in a liquid precursor composition is subjected to ultrasonic treatment.

Furthermore, filamentous nanoparticles and possibly conductive nanowires are preferably used in the method according to the invention according to at least one of the features mentioned above.

Preferably and according to the invention, the intensity of the electric field applied to the hybrid material is from 1 kV / mm to 10 kV / mm.

The invention also extends to the use of such a hybrid material in the manufacture of structural parts and films on a carrier obtained by deposition on all or part of the surface of such a carrier.

In particular, such a hybrid material according to the invention is used to provide:

determining a mechanical stress on the surface of said hybrid material by means of a direct piezoelectric effect; or determining a temperature fluctuation on a surface of said hybrid material by means of a direct pyroelectric effect.

In an embodiment according to the invention, such a hybrid material is used in applications related, for example, to an energy sensor / converter for generating a static or dynamic mechanical wave by means of an inverse piezoelectric effect in applications related to:

flexible audio device and / or

- mechanical drive, and / or

- an anti-icing device, and / or

- mechanical antifouling device.

In another embodiment according to the invention, such a hybrid material is used in applications related to soundproofing material, in particular anechoic material suitable for absorbing the acoustic vibrational wave and dissipating the energy of said vibrational wave through the Joule effect, on a local scale, through conductive nanowires.

The invention also relates to a composite material, to a method for producing such a composite material, and to the use of such a piezoelectric and / or pyroelectric composite solid material, which are characterized in combination by all or some of the features mentioned above or in this work below.

Other objects, features and advantages of the invention will become apparent after reading the following description, which relates to examples that are not intended to limit the invention, and to the accompanying graphic materials, where:

figure 1 presents a descriptive overview diagram of a method for producing a piezoelectric and / or pyroelectric hybrid material according to the invention,

figure 2 presents a schematic cross-sectional view of a piezoelectric and / or pyroelectric hybrid material according to the invention,

3 is a schematic cross-sectional view of an embodiment of a piezoelectric and / or pyroelectric hybrid material according to the invention.

In the method according to the invention shown in FIG. 1, whisker nanoparticles 1, i.e. nanoparticles having a high aspect ratio formed from piezoelectric and / or pyroelectric and / or ferroelectric solid material. Such material is obtained by a method known per se to a person skilled in the art, especially by vapor deposition or by chemical means in the presence of coordination ligands, as described, for example, in Urban et al., (2001) Journal of the American Chemical Society 124 (7 ), 1186-1187 ". In particular, such a method for producing piezoelectric, pyroelectric filiform nanoparticles by the method of electrodeposition in the channels of a porous membrane is described in Example 1 below.

A dispersion of 3 piezoelectric and / or pyroelectric filamentous nanoparticles 1 in a liquid solution 2 of the precursor of a solid dielectric matrix 11 is obtained. Dispersion 3 is obtained by a method known per se to a person skilled in the art, in particular by mechanical stirring or by ultrasonic treatment. In particular, dispersion methods are suitable for forming an isotropic distribution of whisker nanoparticles 1 in a liquid solution 2 of a precursor of a solid dielectric matrix 11 and in a solid dielectric matrix 11. The liquid solution 2 of the precursor of a solid dielectric matrix 11 may be a solution of a thermoplastic polymer in a solvent medium of said polymer.

The hybrid material according to the invention is formed by evaporation of 4 from a liquid solvent medium at a temperature which is higher than the vaporization temperature of said liquid solvent medium. A hybrid material is obtained formed from filiform nanoparticles 1 dispersed in a homogeneous and isotropic manner in a solid dielectric matrix 11.

Then, the step 5 of forming said hybrid material is carried out, mainly by thermoforming the obtained thermoplastic material suitable for providing a sheet of said hybrid material, a film of small thickness from said hybrid material, or alternatively a layer of said hybrid material forming the surface of the carrier 14. The outer surface of the carrier 14 may be of any shape, but in the embodiment shown in FIG. 2 and FIG. 3, the outer surface of the carrier 14 i It wishes to set up a flat.

The hybrid material is then equipped with Appendix 6 with two electrically conductive plates 10, 13 forming two electrodes in contact with the two main sides of the hybrid material, and a potential difference (electrical) suitable to ensure polarization 7 of the composite solid material is applied between the two electrodes. Two electrodes 10, 13 are also suitable for transferring electrical energy from a composite solid material for a direct piezoelectric effect or direct pyroelectric effect. Two electrodes 10, 13 are also suitable for transferring electrical energy to a hybrid material for the inverse piezoelectric effect.

In an embodiment that is not shown, it is also possible that the liquid solution 2 of the precursor of the solid dielectric matrix 11 consists of only one of the components necessary for the polymerization of the thermosetting solid dielectric matrix 11. In this case, the formation of the solid dielectric matrix 11 is obtained by the subsequent addition of other components, necessary for the polymerization of a thermosetting solid dielectric matrix 11 before stage 5 of the formation of the specified hybrid material. The hybrid material according to the invention shown in FIG. 2 contains piezoelectric and / or pyroelectric whisker barium titanate nanoparticles 12 having a high aspect ratio that are distributed homogeneous and isotropically in a thermosetting solid dielectric matrix 11. The barium titanate whisker nanoparticles 12 have an average length over essentially about 10 microns, an average diameter of essentially about 200 nm and an aspect ratio of about 50.

When using the hybrid material according to the invention for direct or reverse piezoelectric applications and for direct pyroelectric applications, the hybrid material forms electrical contact with a flexible polymer substrate 14, which was previously coated with a conductive electrode 13. The piezoelectric and / or pyroelectric hybrid material can additionally be used in the form of a patch , which is subject to fixation on the specified polymer substrate 14.

The hybrid material according to the invention shown in FIG. 3 comprises piezoelectric and / or pyroelectric barium titanate nanoparticles 12 having a high aspect ratio and electrically conductive nanoparticles 15 distributed homogeneous and isotropically in a thermosetting solid dielectric matrix 11. Electrically conductive nanoparticles 15 are selected from conductive nanoparticles, conductive nanowires or carbon nanotubes. The fraction of electrically conductive nanoparticles 15 is selected so that, based on the fraction by volume, it is below the threshold of electrical percolation (above which electrically conductive nanoparticles 15 form an electrically conductive continuous medium in dielectric matrix 11) in the used solid dielectric matrix 11. Hybrid material obtained from thermoplastic matrix 11 subjected to thermoforming on a solid substrate. The hybrid material obtained from the thermosetting matrix 11 is polymerized on a solid substrate that has been previously metallized on a given surface.

In the case where the functional filler of the hybrid material consists of piezoelectric and / or pyroelectric filiform nanoparticles 12 and electrically conductive nanoparticles 15, the vibrations applied to the substrate propagate into the piezoelectric hybrid material. Mechanical waves are converted into electrical energy by means of piezoelectric whisker nanoparticles 12 having a high aspect ratio, and the electric charges generated in this way are scattered by the electrically conductive nanoparticles 15. The propagation of the mechanical wave and substrate vibrations are accordingly suppressed by conversion of the nanoparticles having a high aspect ratio by the inverse piezoelectric effect. , in the form of barium titanate.

EXAMPLE 1

Obtaining nanowires from barium titanate having a high aspect ratio

BaTiO ₃ nanowires are synthesized by electrodeposition of an aqueous solution of barium titanate in the pores of an aluminum oxide filtration membrane (PAA, Porous Anodised Alumina, Whatmann, Cat. No. 6809-5022 or 6809-5002), having a thickness of 50 μm and a porosity of 200 nm. A barium titanate solution is prepared by dissolving 3 g of barium acetate (Cat. No. 255912, Sigma-Aldrich, Lyon, France) and 3.3 g of titanium isopropylate (Cat. No. 377996, Sigma-Aldrich, Lyon, France) in 20, 16 ml of glacial acetic acid (Cat. No. A9967, Sigma-Aldrich, Lyon, France) in the presence of 3.27 ml of ethylene glycol (Cat. No. 324558, Sigma-Aldrich, Lyon, France) and 2 liters of water. The final pH of the resulting solution is 5. The filtration membrane is placed in a solution of barium titanate so that one of the main sides of the filtration membrane is in close contact with the surface of the aluminum sheet, which was previously coated with a conductive layer of silver and which forms the cathode of the electrodeposition device. The anode of the device is formed by a wire of pure metal, for example gold or platinum, which faces the opposite surface of the filtration membrane and is immersed in a solution of barium titanate.

A voltage of 5 V is applied between the cathode and the anode so that the initial electric current intensity approaches 150 μA. Thus, a solution of barium titanate precipitates in the pores of the porous membrane. After the electrodeposition step, a heat treatment step is carried out by annealing the barium titanate nanowires at a temperature of about 600 ° C. in atmospheric air to form ceramic nanowires.

The porous membrane is dissolved by treatment in an aqueous solution of sodium hydroxide at a concentration of 48 g / liter. After a 15-minute treatment, ceramic barium titanate nanowires having a high aspect ratio are released in an alkaline solution. The nanowires are separated from the alkaline solution, washed and stored in an organic solvent, for example N, N-dimethylacetamide (CH ₃ -CO-N (CH ₂ ) ₂ , Cat. No. D5511, Sigma-Aldrich, Lyon, France). Ceramic barium titanate nanowires have an average diameter of approximately 200 nm and an average length of approximately 50 μm for a length-to-diameter ratio (aspect ratio) substantially close to 250.

EXAMPLE 2

Obtaining nanotubes from barium titanate having a high aspect ratio

A BaTiO ₃ solution is prepared as described in Example 1. A BaTiO ₃ solution is deposited on one of the main surfaces of an aluminum oxide (PAA) filtration membrane having a thickness of 50 μm and a porosity of 200 nm, so that a layer is formed that covers the inner pore surface of the specified filtration membrane . The porous membrane is dried at a temperature of 100 ° C and then carry out the stage of heat treatment by annealing the nanotubes from BaTiO ₃ at a temperature of approximately 600 ° C in atmospheric air. The alkaline treatment of the porous membrane and then washing are carried out as described in Example 1, in order to form a suspension of BaTiO ₃ nanotubes in an organic solvent, for example N, N-dimethylacetamide.

EXAMPLE 3

Obtaining a piezoelectric and / or pyroelectric composite hybrid material formed from BaTiO ₃ nanowires dispersed in a thermoplastic dielectric matrix 11 from polyamide 11

250 mg of BaTiO ₃ nanowires having an aspect ratio of 25, as described in Example 1, are dispersed in 20 ml of N, N-dimethylacetamide. The dispersion is subjected to dispersion treatment in an ultrasonic bath having a frequency of substantially approximately 20 kHz for a dissipated power of approximately 500 watts. On the other hand, 250 mg of polyamide 11 (PA11, Rilsan® polyamide 11, ARKEMA, USA) was dissolved in 20 ml of N, N-dimethylacetamide. The mixture is homogenized by ultrasonic treatment. After evaporation of N, N-dimethylacetamide and hot thermoforming, a composite hybrid film having a thickness of 150 μm is obtained in which the load of filamentous BaTiO ₃ nanoparticles in the matrix of polyamide 11 is 12% by volume.

In one embodiment, the film of the composite hybrid material is deposited in the form of a patch on the surface of the substrate at ambient temperature, or alternatively it is formed by heat treatment on the surface of the electrically conductive substrate.

An electrode is placed on each of the two main sides of the obtained film of the composite hybrid material, and the composite hybrid material is subjected to polarization treatment by applying an electric field having an intensity of 3 kV / mm at a temperature of 100 ° C for 30 minutes.

A composite hybrid material according to the invention is obtained having a dielectric constant approaching 5, a pyroelectric efficiency index F of more than 0.7 μC / K / m ² and a piezoelectric efficiency index d _{33 of} more than 45 mV · m / N, with substantially maintaining the mechanical ductility of the matrix 11 of polyamide.

The application of mechanical compression stress to the surface of a solid composite material or torsional stress induces a change in the macroscopic dipole of the composite solid material. Therefore, such materials can be used as shock or deformation sensors or in systems for converting mechanical energy into electrical energy.

The application of temperature fluctuations to the surface of a composite solid hybrid material according to the invention induces a change in the macroscopic dipole of said composite solid material. Therefore, such materials can preferably be used as thermal sensors or in systems for converting thermal energy into electrical energy.

Applying a voltage, either constant or alternating, to the two main sides of the composite solid hybrid material according to the invention induces deformation of said material, generating surface tension. Therefore, such materials can preferably be used as sensors for converting electrical energy into mechanical energy.

EXAMPLE 4

Obtaining a piezoelectric and / or pyroelectric composite solid hybrid material formed from BaTiO ₃ nanowires in a thermosetting polyurethane matrix

132 mg of ceramic nanowires (BaTiO ₃ ) having an aspect ratio of 25, as described in Example 1, are dispersed in 100 mg of acrylic resin (Maraiego, Pamiers, France). A suspension of ceramic nanowires in acrylic resin is subjected to ultrasonic treatment at a frequency of 50 kHz at a power of 500 watts. 32 mg of isocyanate is introduced into the suspension (Maraiego, Pamiers, France). The mixture is homogenized by ultrasound. The solution is then precipitated on an electrically conductive substrate. After polymerization, a film is made of a piezoelectric and pyroelectric composite solid hybrid material having a thickness of 100 μm and a load at 12% by volume.

The electrode is placed on the main side of the composite solid hybrid film opposite the electrically conductive substrate, and an electric field of 3 kV / mm is applied to said hybrid solid composite material at a temperature of 100 ° C. for 30 minutes. Thus, a composite solid hybrid material having a permittivity approaching 5 is obtained by polarization, a pyroelectric efficiency index F of more than 0.7 μC / K / m ² and a piezoelectric efficiency index d _{33 of} more than 45 mV · m / N.

As an illustrative example of the electroactive material of the prior art, for comparison with the characteristics of the composite solid hybrid material according to the invention described in Examples 3 and 4, barium titanate ceramic has a pyroelectric efficiency value of F0.15 μC / K / m ² , a piezoelectric value performance indicator d ₃₃ 15 mV · m / N. Such a ferroelectric barium titanate ceramic has high mechanical fragility.

The application of mechanical stress to the surface of a composite solid hybrid material induces a change in the macroscopic dipole of the composite solid material. Therefore, such materials can be used as shock or deformation sensors or in systems for converting mechanical energy into electrical energy.

The application of temperature fluctuations to the surface of a composite solid hybrid material induces a change in the macroscopic dipole of the specified material. Therefore, such a material can preferably be used as thermal sensors or in systems for converting thermal energy into electrical energy.

EXAMPLE 5

Obtaining a flexible acoustic device from a composite material formed from piezoelectric nanowires having a high aspect ratio dispersed in a polymer matrix

The hybrid material according to the invention is obtained in accordance with Example 3. The hybrid material obtained from the thermoplastic matrix of polyamide 11 is thermoformed on a flexible polymer substrate (polyethylene) having a thickness of 70 μm and a size of 1 m × 1 m

You can adjust the electrical resistance of the hybrid material applied to the substrate by changing the layer thickness of the specified material and the surface area onto which the hybrid material is deposited, so that the electrical resistance of the hybrid material adapts to the electrical resistance of the voltage generator.

A voltage of 5 V and a variable frequency from 500 Hz to 20 kHz are applied to the two main sides of the composite solid hybrid material according to the invention. Deformation of a composite solid hybrid material and substrate under the influence of an electric field induces a voltage on the surface of the acoustic device that has a frequency equal to the frequency of the applied field and produces an audible sound.

Since the plasticity of the matrix of the solid composite material and the polymer substrate is preserved and the energy consumption of the system is low, a flexible acoustic device is an alternative to the use of traditional electromagnetic reflectors.

EXAMPLE 6

Obtaining a flexible acoustic device from a hybrid material formed from piezoelectric nanowires having a high aspect ratio dispersed in a thermosetting polyurethane matrix

The composite solid hybrid material according to the invention is obtained in accordance with Example 4. A composite solid hybrid material obtained from a thermosetting polyurethane matrix is applied to polymerize it onto a flexible polyethylene substrate having a thickness of 70 μm and a size of 1 m × 1 m that has previously been metallized on the surface to which the specified composite solid hybrid material is applied. An acoustic device according to the invention is obtained in accordance with the method described in Example 5.

EXAMPLE 7

Obtaining a piezoelectric and / or pyroelectric composite solid hybrid material formed from NaNbO _3l nanowires in a thermoplastic polyamide matrix

Nanowires of sodium niobate NaNbO ₃ was synthesized by dissolving 1 g of niobium pentoxide in 60 ml of sodium hydroxide at a concentration of 10 mM, and the resulting solution was treated in an autoclave having a capacity of 25 ml, at 180 ° C for 8 hours. Get filamentary nanoparticles (nanowires) having an aspect ratio of more than 30 and an off-center-symmetric orthorhombic crystal structure.

100 mg of NaNbO ₃ nanowires are mixed with 20 ml of N, N-dimethylacetamide. The resulting suspension is sonicated (frequency approximately 20 kHz) for a dissipated power of approximately 500 watts. In addition, 200 mg of polyamide 11 is dissolved in 20 ml of N, N-dimethylacetamide. A solution containing nanowires of NaNbO ₃ and a solution of polyamide 11 are mixed, and the resulting mixture is homogenized by ultrasound. N, N-dimethylacetamide was evaporated. The step of hot thermoforming the composite solid material is carried out in order to form a composite film having a thickness of 30 μm to 1 mm. The fraction by volume of the inorganic phase in the dielectric matrix is 10%.

A conductive electrode is deposited on each of the main sides of the composite film and an electric field of 10 kV / mm is applied at a temperature of 130 ° C for 10 minutes. A piezoelectric and / or pyroelectric composite film is obtained having piezoelectric and / or pyroelectric properties in the temperature range from -100 ° C to + 180 ° C.

Claims (21)

1. A piezoelectric and / or pyroelectric composite solid material called a hybrid material, containing:
- solid dielectric matrix (11),
- an inorganic filler distributed in a solid dielectric matrix (11), where the inorganic filler consists of a material selected from the group consisting of piezoelectric materials, pyroelectric materials and piezoelectric and pyroelectric materials,
in which the inorganic filler contains solid nanoparticles called filamentous nanoparticles (12), having:
- length, continuing in the main direction of elongation of filiform nanoparticles (12),
- two sizes, called orthogonal sizes, continuing in two transverse directions, which are mutually perpendicular and orthogonal to the main direction of elongation of the filamentous nanoparticles (12), where the orthogonal dimensions are less than the length and less than 500 nm, and
- two ratios, called aspect ratios, between the length and each of the two orthogonal dimensions, where the aspect ratios are more than 10,
Where
- whisker nanoparticles (12) are distributed in the volume of the solid dielectric matrix (11) in an amount by volume of less than 50%, and where
- the main directions of elongation of filamentous nanoparticles (12) of the inorganic filler distributed in the dielectric matrix (11) have a substantially isotropic distribution in the solid dielectric matrix (11). 2. The material according to claim 1, where the inorganic filler is distributed substantially uniformly in the solid dielectric matrix (11). 3. The material according to claim 1, where the filamentary nanoparticles (12) are selected from the group consisting of nanowires, nanorods and nanotubes. 4. The material according to claim 1, where the filamentary nanoparticles (12) have a length of more than 1 μm. 5. The material according to claim 1, where the inorganic filler is formed from a material selected from the group of inorganic ceramics. 6. The material according to claim 1, where the solid dielectric matrix (11) contains at least one polymer material selected from the group consisting of thermoplastic polymer materials and thermosetting polymer materials. 7. The material according to claim 1, where it further comprises a filler, called a conductive filler, from an electrically conductive material containing conductive nanowires (15), having:
- the length, continuing in the main direction of elongation of the conductive nanowires (15),
- two sizes, called orthogonal dimensions, continuing in two transverse directions, which are mutually perpendicular and orthogonal to the main direction of elongation of the conductive nanowires (15), where the orthogonal dimensions are less than the length and less than 500 nm, and
- two ratios, called aspect ratios, between the length and each of the two orthogonal dimensions of the conductive nanowires (15), where the aspect ratios are more than 50,
in which the conductive nanowires (15) are distributed in the volume of the solid dielectric matrix (11) in an amount by volume of less than 1%. 8. A method for producing a composite solid material called a hybrid material, where a dispersion of an inorganic filler containing filamentous nanoparticles (12) is formed from an inorganic material selected from the group consisting of piezoelectric materials, pyroelectric materials and piezoelectric and pyroelectric materials, where filamentous nanoparticles (12) have:
- length, continuing in the main direction of elongation of filiform nanoparticles (12),
- two sizes, called orthogonal sizes, continuing in two transverse directions, which are mutually perpendicular and orthogonal to the main direction of elongation of the filamentous nanoparticles (12), where the orthogonal dimensions are less than the length and less than 500 nm, and
- two ratios, called aspect ratios, between the length and each of the two orthogonal dimensions, where the aspect ratios are more than 10,
in the liquid composition (2) of the precursor of the solid dielectric matrix (11) so as to obtain an amount by volume of filamentous nanoparticles (12) in the hybrid material less than 50%, and so that the main directions of elongation of filamentous nanoparticles (12) of an inorganic filler distributed in the dielectric matrix (11), had a substantially isotropic distribution in the solid dielectric matrix (11). 9. The method of claim 8, where
- a dispersion of filamentous nanoparticles (12) is obtained in a liquid solvent medium,
- the dispersion is mixed into the liquid composition (2) of the precursor,
the liquid solvent is removed, and
- the hybrid material is placed in an electric field suitable for polarizing filamentary nanoparticles (12) and converting them into piezoelectric and / or pyroelectric filamentous nanoparticles (12). 10. The method according to claim 8, where when the solid dielectric matrix (11) contains at least one polymeric material, then the precursor liquid composition (2) is a solution of the polymeric material in a liquid solvent selected from a filament dispersion solvent (12) and solvents that are mixed with a solvent of a dispersion of whisker nanoparticles (12). 11. The method according to claim 8, where when the solid dielectric matrix (11) contains at least one thermoplastic material, then the liquid precursor composition (2) is formed from the solid dielectric matrix (11) in the molten state. 12. The method according to claim 8, where when the solid dielectric matrix (11) contains at least one thermosetting material, then the liquid precursor composition (2) is formed from at least one liquid composition included in the thermosetting material composition. 13. The method according to claim 8, where the dispersion of the filamentary nanoparticles (1) in the liquid composition (2) of the precursor is subjected to ultrasound treatment. 14. The method of claim 8, where the intensity of the electric field applied to the hybrid material is from 1 kV / mm to 10 kV / mm. 15. The use of the hybrid material according to any one of claims 1 to 7 in the manufacture of structural parts and films on a carrier obtained by deposition on all or part of the surface of such a carrier. 16. The use according to claim 15 of a hybrid material for determining mechanical stresses on a surface of a hybrid material by means of a direct piezoelectric effect or for determining temperature fluctuations on a surface of a hybrid material by means of a direct pyroelectric effect. 17. The application of clause 15 of the hybrid material, where the hybrid material allows you to create a static or dynamic mechanical wave through the inverse piezoelectric effect. 18. The use of hybrid material according to 17 in an audio device, especially in a flexible audio device. 19. The use of the hybrid material according to 17 in an anti-icing device. 20. The use of a hybrid material according to 17 in a mechanical antifouling device. 21. The use according to claim 15 of the hybrid material according to claim 7 in the manufacture of a soundproof material suitable for absorbing an acoustic vibrational wave and scattering the energy of the vibrational wave through the Joule effect.

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